1 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com 2 * Copyright (c) 2016 Facebook 3 * 4 * This program is free software; you can redistribute it and/or 5 * modify it under the terms of version 2 of the GNU General Public 6 * License as published by the Free Software Foundation. 7 * 8 * This program is distributed in the hope that it will be useful, but 9 * WITHOUT ANY WARRANTY; without even the implied warranty of 10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 11 * General Public License for more details. 12 */ 13 #include <linux/kernel.h> 14 #include <linux/types.h> 15 #include <linux/slab.h> 16 #include <linux/bpf.h> 17 #include <linux/filter.h> 18 #include <net/netlink.h> 19 #include <linux/file.h> 20 #include <linux/vmalloc.h> 21 22 /* bpf_check() is a static code analyzer that walks eBPF program 23 * instruction by instruction and updates register/stack state. 24 * All paths of conditional branches are analyzed until 'bpf_exit' insn. 25 * 26 * The first pass is depth-first-search to check that the program is a DAG. 27 * It rejects the following programs: 28 * - larger than BPF_MAXINSNS insns 29 * - if loop is present (detected via back-edge) 30 * - unreachable insns exist (shouldn't be a forest. program = one function) 31 * - out of bounds or malformed jumps 32 * The second pass is all possible path descent from the 1st insn. 33 * Since it's analyzing all pathes through the program, the length of the 34 * analysis is limited to 32k insn, which may be hit even if total number of 35 * insn is less then 4K, but there are too many branches that change stack/regs. 36 * Number of 'branches to be analyzed' is limited to 1k 37 * 38 * On entry to each instruction, each register has a type, and the instruction 39 * changes the types of the registers depending on instruction semantics. 40 * If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is 41 * copied to R1. 42 * 43 * All registers are 64-bit. 44 * R0 - return register 45 * R1-R5 argument passing registers 46 * R6-R9 callee saved registers 47 * R10 - frame pointer read-only 48 * 49 * At the start of BPF program the register R1 contains a pointer to bpf_context 50 * and has type PTR_TO_CTX. 51 * 52 * Verifier tracks arithmetic operations on pointers in case: 53 * BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), 54 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20), 55 * 1st insn copies R10 (which has FRAME_PTR) type into R1 56 * and 2nd arithmetic instruction is pattern matched to recognize 57 * that it wants to construct a pointer to some element within stack. 58 * So after 2nd insn, the register R1 has type PTR_TO_STACK 59 * (and -20 constant is saved for further stack bounds checking). 60 * Meaning that this reg is a pointer to stack plus known immediate constant. 61 * 62 * Most of the time the registers have UNKNOWN_VALUE type, which 63 * means the register has some value, but it's not a valid pointer. 64 * (like pointer plus pointer becomes UNKNOWN_VALUE type) 65 * 66 * When verifier sees load or store instructions the type of base register 67 * can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, FRAME_PTR. These are three pointer 68 * types recognized by check_mem_access() function. 69 * 70 * PTR_TO_MAP_VALUE means that this register is pointing to 'map element value' 71 * and the range of [ptr, ptr + map's value_size) is accessible. 72 * 73 * registers used to pass values to function calls are checked against 74 * function argument constraints. 75 * 76 * ARG_PTR_TO_MAP_KEY is one of such argument constraints. 77 * It means that the register type passed to this function must be 78 * PTR_TO_STACK and it will be used inside the function as 79 * 'pointer to map element key' 80 * 81 * For example the argument constraints for bpf_map_lookup_elem(): 82 * .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL, 83 * .arg1_type = ARG_CONST_MAP_PTR, 84 * .arg2_type = ARG_PTR_TO_MAP_KEY, 85 * 86 * ret_type says that this function returns 'pointer to map elem value or null' 87 * function expects 1st argument to be a const pointer to 'struct bpf_map' and 88 * 2nd argument should be a pointer to stack, which will be used inside 89 * the helper function as a pointer to map element key. 90 * 91 * On the kernel side the helper function looks like: 92 * u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) 93 * { 94 * struct bpf_map *map = (struct bpf_map *) (unsigned long) r1; 95 * void *key = (void *) (unsigned long) r2; 96 * void *value; 97 * 98 * here kernel can access 'key' and 'map' pointers safely, knowing that 99 * [key, key + map->key_size) bytes are valid and were initialized on 100 * the stack of eBPF program. 101 * } 102 * 103 * Corresponding eBPF program may look like: 104 * BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), // after this insn R2 type is FRAME_PTR 105 * BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK 106 * BPF_LD_MAP_FD(BPF_REG_1, map_fd), // after this insn R1 type is CONST_PTR_TO_MAP 107 * BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), 108 * here verifier looks at prototype of map_lookup_elem() and sees: 109 * .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok, 110 * Now verifier knows that this map has key of R1->map_ptr->key_size bytes 111 * 112 * Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far, 113 * Now verifier checks that [R2, R2 + map's key_size) are within stack limits 114 * and were initialized prior to this call. 115 * If it's ok, then verifier allows this BPF_CALL insn and looks at 116 * .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets 117 * R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function 118 * returns ether pointer to map value or NULL. 119 * 120 * When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off' 121 * insn, the register holding that pointer in the true branch changes state to 122 * PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false 123 * branch. See check_cond_jmp_op(). 124 * 125 * After the call R0 is set to return type of the function and registers R1-R5 126 * are set to NOT_INIT to indicate that they are no longer readable. 127 */ 128 129 /* types of values stored in eBPF registers */ 130 enum bpf_reg_type { 131 NOT_INIT = 0, /* nothing was written into register */ 132 UNKNOWN_VALUE, /* reg doesn't contain a valid pointer */ 133 PTR_TO_CTX, /* reg points to bpf_context */ 134 CONST_PTR_TO_MAP, /* reg points to struct bpf_map */ 135 PTR_TO_MAP_VALUE, /* reg points to map element value */ 136 PTR_TO_MAP_VALUE_OR_NULL,/* points to map elem value or NULL */ 137 FRAME_PTR, /* reg == frame_pointer */ 138 PTR_TO_STACK, /* reg == frame_pointer + imm */ 139 CONST_IMM, /* constant integer value */ 140 141 /* PTR_TO_PACKET represents: 142 * skb->data 143 * skb->data + imm 144 * skb->data + (u16) var 145 * skb->data + (u16) var + imm 146 * if (range > 0) then [ptr, ptr + range - off) is safe to access 147 * if (id > 0) means that some 'var' was added 148 * if (off > 0) menas that 'imm' was added 149 */ 150 PTR_TO_PACKET, 151 PTR_TO_PACKET_END, /* skb->data + headlen */ 152 }; 153 154 struct reg_state { 155 enum bpf_reg_type type; 156 union { 157 /* valid when type == CONST_IMM | PTR_TO_STACK | UNKNOWN_VALUE */ 158 s64 imm; 159 160 /* valid when type == PTR_TO_PACKET* */ 161 struct { 162 u32 id; 163 u16 off; 164 u16 range; 165 }; 166 167 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE | 168 * PTR_TO_MAP_VALUE_OR_NULL 169 */ 170 struct bpf_map *map_ptr; 171 }; 172 }; 173 174 enum bpf_stack_slot_type { 175 STACK_INVALID, /* nothing was stored in this stack slot */ 176 STACK_SPILL, /* register spilled into stack */ 177 STACK_MISC /* BPF program wrote some data into this slot */ 178 }; 179 180 #define BPF_REG_SIZE 8 /* size of eBPF register in bytes */ 181 182 /* state of the program: 183 * type of all registers and stack info 184 */ 185 struct verifier_state { 186 struct reg_state regs[MAX_BPF_REG]; 187 u8 stack_slot_type[MAX_BPF_STACK]; 188 struct reg_state spilled_regs[MAX_BPF_STACK / BPF_REG_SIZE]; 189 }; 190 191 /* linked list of verifier states used to prune search */ 192 struct verifier_state_list { 193 struct verifier_state state; 194 struct verifier_state_list *next; 195 }; 196 197 /* verifier_state + insn_idx are pushed to stack when branch is encountered */ 198 struct verifier_stack_elem { 199 /* verifer state is 'st' 200 * before processing instruction 'insn_idx' 201 * and after processing instruction 'prev_insn_idx' 202 */ 203 struct verifier_state st; 204 int insn_idx; 205 int prev_insn_idx; 206 struct verifier_stack_elem *next; 207 }; 208 209 #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */ 210 211 /* single container for all structs 212 * one verifier_env per bpf_check() call 213 */ 214 struct verifier_env { 215 struct bpf_prog *prog; /* eBPF program being verified */ 216 struct verifier_stack_elem *head; /* stack of verifier states to be processed */ 217 int stack_size; /* number of states to be processed */ 218 struct verifier_state cur_state; /* current verifier state */ 219 struct verifier_state_list **explored_states; /* search pruning optimization */ 220 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */ 221 u32 used_map_cnt; /* number of used maps */ 222 bool allow_ptr_leaks; 223 }; 224 225 #define BPF_COMPLEXITY_LIMIT_INSNS 65536 226 #define BPF_COMPLEXITY_LIMIT_STACK 1024 227 228 struct bpf_call_arg_meta { 229 struct bpf_map *map_ptr; 230 bool raw_mode; 231 int regno; 232 int access_size; 233 }; 234 235 /* verbose verifier prints what it's seeing 236 * bpf_check() is called under lock, so no race to access these global vars 237 */ 238 static u32 log_level, log_size, log_len; 239 static char *log_buf; 240 241 static DEFINE_MUTEX(bpf_verifier_lock); 242 243 /* log_level controls verbosity level of eBPF verifier. 244 * verbose() is used to dump the verification trace to the log, so the user 245 * can figure out what's wrong with the program 246 */ 247 static __printf(1, 2) void verbose(const char *fmt, ...) 248 { 249 va_list args; 250 251 if (log_level == 0 || log_len >= log_size - 1) 252 return; 253 254 va_start(args, fmt); 255 log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args); 256 va_end(args); 257 } 258 259 /* string representation of 'enum bpf_reg_type' */ 260 static const char * const reg_type_str[] = { 261 [NOT_INIT] = "?", 262 [UNKNOWN_VALUE] = "inv", 263 [PTR_TO_CTX] = "ctx", 264 [CONST_PTR_TO_MAP] = "map_ptr", 265 [PTR_TO_MAP_VALUE] = "map_value", 266 [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null", 267 [FRAME_PTR] = "fp", 268 [PTR_TO_STACK] = "fp", 269 [CONST_IMM] = "imm", 270 [PTR_TO_PACKET] = "pkt", 271 [PTR_TO_PACKET_END] = "pkt_end", 272 }; 273 274 static void print_verifier_state(struct verifier_state *state) 275 { 276 struct reg_state *reg; 277 enum bpf_reg_type t; 278 int i; 279 280 for (i = 0; i < MAX_BPF_REG; i++) { 281 reg = &state->regs[i]; 282 t = reg->type; 283 if (t == NOT_INIT) 284 continue; 285 verbose(" R%d=%s", i, reg_type_str[t]); 286 if (t == CONST_IMM || t == PTR_TO_STACK) 287 verbose("%lld", reg->imm); 288 else if (t == PTR_TO_PACKET) 289 verbose("(id=%d,off=%d,r=%d)", 290 reg->id, reg->off, reg->range); 291 else if (t == UNKNOWN_VALUE && reg->imm) 292 verbose("%lld", reg->imm); 293 else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE || 294 t == PTR_TO_MAP_VALUE_OR_NULL) 295 verbose("(ks=%d,vs=%d)", 296 reg->map_ptr->key_size, 297 reg->map_ptr->value_size); 298 } 299 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 300 if (state->stack_slot_type[i] == STACK_SPILL) 301 verbose(" fp%d=%s", -MAX_BPF_STACK + i, 302 reg_type_str[state->spilled_regs[i / BPF_REG_SIZE].type]); 303 } 304 verbose("\n"); 305 } 306 307 static const char *const bpf_class_string[] = { 308 [BPF_LD] = "ld", 309 [BPF_LDX] = "ldx", 310 [BPF_ST] = "st", 311 [BPF_STX] = "stx", 312 [BPF_ALU] = "alu", 313 [BPF_JMP] = "jmp", 314 [BPF_RET] = "BUG", 315 [BPF_ALU64] = "alu64", 316 }; 317 318 static const char *const bpf_alu_string[16] = { 319 [BPF_ADD >> 4] = "+=", 320 [BPF_SUB >> 4] = "-=", 321 [BPF_MUL >> 4] = "*=", 322 [BPF_DIV >> 4] = "/=", 323 [BPF_OR >> 4] = "|=", 324 [BPF_AND >> 4] = "&=", 325 [BPF_LSH >> 4] = "<<=", 326 [BPF_RSH >> 4] = ">>=", 327 [BPF_NEG >> 4] = "neg", 328 [BPF_MOD >> 4] = "%=", 329 [BPF_XOR >> 4] = "^=", 330 [BPF_MOV >> 4] = "=", 331 [BPF_ARSH >> 4] = "s>>=", 332 [BPF_END >> 4] = "endian", 333 }; 334 335 static const char *const bpf_ldst_string[] = { 336 [BPF_W >> 3] = "u32", 337 [BPF_H >> 3] = "u16", 338 [BPF_B >> 3] = "u8", 339 [BPF_DW >> 3] = "u64", 340 }; 341 342 static const char *const bpf_jmp_string[16] = { 343 [BPF_JA >> 4] = "jmp", 344 [BPF_JEQ >> 4] = "==", 345 [BPF_JGT >> 4] = ">", 346 [BPF_JGE >> 4] = ">=", 347 [BPF_JSET >> 4] = "&", 348 [BPF_JNE >> 4] = "!=", 349 [BPF_JSGT >> 4] = "s>", 350 [BPF_JSGE >> 4] = "s>=", 351 [BPF_CALL >> 4] = "call", 352 [BPF_EXIT >> 4] = "exit", 353 }; 354 355 static void print_bpf_insn(struct bpf_insn *insn) 356 { 357 u8 class = BPF_CLASS(insn->code); 358 359 if (class == BPF_ALU || class == BPF_ALU64) { 360 if (BPF_SRC(insn->code) == BPF_X) 361 verbose("(%02x) %sr%d %s %sr%d\n", 362 insn->code, class == BPF_ALU ? "(u32) " : "", 363 insn->dst_reg, 364 bpf_alu_string[BPF_OP(insn->code) >> 4], 365 class == BPF_ALU ? "(u32) " : "", 366 insn->src_reg); 367 else 368 verbose("(%02x) %sr%d %s %s%d\n", 369 insn->code, class == BPF_ALU ? "(u32) " : "", 370 insn->dst_reg, 371 bpf_alu_string[BPF_OP(insn->code) >> 4], 372 class == BPF_ALU ? "(u32) " : "", 373 insn->imm); 374 } else if (class == BPF_STX) { 375 if (BPF_MODE(insn->code) == BPF_MEM) 376 verbose("(%02x) *(%s *)(r%d %+d) = r%d\n", 377 insn->code, 378 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 379 insn->dst_reg, 380 insn->off, insn->src_reg); 381 else if (BPF_MODE(insn->code) == BPF_XADD) 382 verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n", 383 insn->code, 384 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 385 insn->dst_reg, insn->off, 386 insn->src_reg); 387 else 388 verbose("BUG_%02x\n", insn->code); 389 } else if (class == BPF_ST) { 390 if (BPF_MODE(insn->code) != BPF_MEM) { 391 verbose("BUG_st_%02x\n", insn->code); 392 return; 393 } 394 verbose("(%02x) *(%s *)(r%d %+d) = %d\n", 395 insn->code, 396 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 397 insn->dst_reg, 398 insn->off, insn->imm); 399 } else if (class == BPF_LDX) { 400 if (BPF_MODE(insn->code) != BPF_MEM) { 401 verbose("BUG_ldx_%02x\n", insn->code); 402 return; 403 } 404 verbose("(%02x) r%d = *(%s *)(r%d %+d)\n", 405 insn->code, insn->dst_reg, 406 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 407 insn->src_reg, insn->off); 408 } else if (class == BPF_LD) { 409 if (BPF_MODE(insn->code) == BPF_ABS) { 410 verbose("(%02x) r0 = *(%s *)skb[%d]\n", 411 insn->code, 412 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 413 insn->imm); 414 } else if (BPF_MODE(insn->code) == BPF_IND) { 415 verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n", 416 insn->code, 417 bpf_ldst_string[BPF_SIZE(insn->code) >> 3], 418 insn->src_reg, insn->imm); 419 } else if (BPF_MODE(insn->code) == BPF_IMM) { 420 verbose("(%02x) r%d = 0x%x\n", 421 insn->code, insn->dst_reg, insn->imm); 422 } else { 423 verbose("BUG_ld_%02x\n", insn->code); 424 return; 425 } 426 } else if (class == BPF_JMP) { 427 u8 opcode = BPF_OP(insn->code); 428 429 if (opcode == BPF_CALL) { 430 verbose("(%02x) call %d\n", insn->code, insn->imm); 431 } else if (insn->code == (BPF_JMP | BPF_JA)) { 432 verbose("(%02x) goto pc%+d\n", 433 insn->code, insn->off); 434 } else if (insn->code == (BPF_JMP | BPF_EXIT)) { 435 verbose("(%02x) exit\n", insn->code); 436 } else if (BPF_SRC(insn->code) == BPF_X) { 437 verbose("(%02x) if r%d %s r%d goto pc%+d\n", 438 insn->code, insn->dst_reg, 439 bpf_jmp_string[BPF_OP(insn->code) >> 4], 440 insn->src_reg, insn->off); 441 } else { 442 verbose("(%02x) if r%d %s 0x%x goto pc%+d\n", 443 insn->code, insn->dst_reg, 444 bpf_jmp_string[BPF_OP(insn->code) >> 4], 445 insn->imm, insn->off); 446 } 447 } else { 448 verbose("(%02x) %s\n", insn->code, bpf_class_string[class]); 449 } 450 } 451 452 static int pop_stack(struct verifier_env *env, int *prev_insn_idx) 453 { 454 struct verifier_stack_elem *elem; 455 int insn_idx; 456 457 if (env->head == NULL) 458 return -1; 459 460 memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state)); 461 insn_idx = env->head->insn_idx; 462 if (prev_insn_idx) 463 *prev_insn_idx = env->head->prev_insn_idx; 464 elem = env->head->next; 465 kfree(env->head); 466 env->head = elem; 467 env->stack_size--; 468 return insn_idx; 469 } 470 471 static struct verifier_state *push_stack(struct verifier_env *env, int insn_idx, 472 int prev_insn_idx) 473 { 474 struct verifier_stack_elem *elem; 475 476 elem = kmalloc(sizeof(struct verifier_stack_elem), GFP_KERNEL); 477 if (!elem) 478 goto err; 479 480 memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state)); 481 elem->insn_idx = insn_idx; 482 elem->prev_insn_idx = prev_insn_idx; 483 elem->next = env->head; 484 env->head = elem; 485 env->stack_size++; 486 if (env->stack_size > BPF_COMPLEXITY_LIMIT_STACK) { 487 verbose("BPF program is too complex\n"); 488 goto err; 489 } 490 return &elem->st; 491 err: 492 /* pop all elements and return */ 493 while (pop_stack(env, NULL) >= 0); 494 return NULL; 495 } 496 497 #define CALLER_SAVED_REGS 6 498 static const int caller_saved[CALLER_SAVED_REGS] = { 499 BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5 500 }; 501 502 static void init_reg_state(struct reg_state *regs) 503 { 504 int i; 505 506 for (i = 0; i < MAX_BPF_REG; i++) { 507 regs[i].type = NOT_INIT; 508 regs[i].imm = 0; 509 } 510 511 /* frame pointer */ 512 regs[BPF_REG_FP].type = FRAME_PTR; 513 514 /* 1st arg to a function */ 515 regs[BPF_REG_1].type = PTR_TO_CTX; 516 } 517 518 static void mark_reg_unknown_value(struct reg_state *regs, u32 regno) 519 { 520 BUG_ON(regno >= MAX_BPF_REG); 521 regs[regno].type = UNKNOWN_VALUE; 522 regs[regno].imm = 0; 523 } 524 525 enum reg_arg_type { 526 SRC_OP, /* register is used as source operand */ 527 DST_OP, /* register is used as destination operand */ 528 DST_OP_NO_MARK /* same as above, check only, don't mark */ 529 }; 530 531 static int check_reg_arg(struct reg_state *regs, u32 regno, 532 enum reg_arg_type t) 533 { 534 if (regno >= MAX_BPF_REG) { 535 verbose("R%d is invalid\n", regno); 536 return -EINVAL; 537 } 538 539 if (t == SRC_OP) { 540 /* check whether register used as source operand can be read */ 541 if (regs[regno].type == NOT_INIT) { 542 verbose("R%d !read_ok\n", regno); 543 return -EACCES; 544 } 545 } else { 546 /* check whether register used as dest operand can be written to */ 547 if (regno == BPF_REG_FP) { 548 verbose("frame pointer is read only\n"); 549 return -EACCES; 550 } 551 if (t == DST_OP) 552 mark_reg_unknown_value(regs, regno); 553 } 554 return 0; 555 } 556 557 static int bpf_size_to_bytes(int bpf_size) 558 { 559 if (bpf_size == BPF_W) 560 return 4; 561 else if (bpf_size == BPF_H) 562 return 2; 563 else if (bpf_size == BPF_B) 564 return 1; 565 else if (bpf_size == BPF_DW) 566 return 8; 567 else 568 return -EINVAL; 569 } 570 571 static bool is_spillable_regtype(enum bpf_reg_type type) 572 { 573 switch (type) { 574 case PTR_TO_MAP_VALUE: 575 case PTR_TO_MAP_VALUE_OR_NULL: 576 case PTR_TO_STACK: 577 case PTR_TO_CTX: 578 case PTR_TO_PACKET: 579 case PTR_TO_PACKET_END: 580 case FRAME_PTR: 581 case CONST_PTR_TO_MAP: 582 return true; 583 default: 584 return false; 585 } 586 } 587 588 /* check_stack_read/write functions track spill/fill of registers, 589 * stack boundary and alignment are checked in check_mem_access() 590 */ 591 static int check_stack_write(struct verifier_state *state, int off, int size, 592 int value_regno) 593 { 594 int i; 595 /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0, 596 * so it's aligned access and [off, off + size) are within stack limits 597 */ 598 599 if (value_regno >= 0 && 600 is_spillable_regtype(state->regs[value_regno].type)) { 601 602 /* register containing pointer is being spilled into stack */ 603 if (size != BPF_REG_SIZE) { 604 verbose("invalid size of register spill\n"); 605 return -EACCES; 606 } 607 608 /* save register state */ 609 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = 610 state->regs[value_regno]; 611 612 for (i = 0; i < BPF_REG_SIZE; i++) 613 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL; 614 } else { 615 /* regular write of data into stack */ 616 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = 617 (struct reg_state) {}; 618 619 for (i = 0; i < size; i++) 620 state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC; 621 } 622 return 0; 623 } 624 625 static int check_stack_read(struct verifier_state *state, int off, int size, 626 int value_regno) 627 { 628 u8 *slot_type; 629 int i; 630 631 slot_type = &state->stack_slot_type[MAX_BPF_STACK + off]; 632 633 if (slot_type[0] == STACK_SPILL) { 634 if (size != BPF_REG_SIZE) { 635 verbose("invalid size of register spill\n"); 636 return -EACCES; 637 } 638 for (i = 1; i < BPF_REG_SIZE; i++) { 639 if (slot_type[i] != STACK_SPILL) { 640 verbose("corrupted spill memory\n"); 641 return -EACCES; 642 } 643 } 644 645 if (value_regno >= 0) 646 /* restore register state from stack */ 647 state->regs[value_regno] = 648 state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE]; 649 return 0; 650 } else { 651 for (i = 0; i < size; i++) { 652 if (slot_type[i] != STACK_MISC) { 653 verbose("invalid read from stack off %d+%d size %d\n", 654 off, i, size); 655 return -EACCES; 656 } 657 } 658 if (value_regno >= 0) 659 /* have read misc data from the stack */ 660 mark_reg_unknown_value(state->regs, value_regno); 661 return 0; 662 } 663 } 664 665 /* check read/write into map element returned by bpf_map_lookup_elem() */ 666 static int check_map_access(struct verifier_env *env, u32 regno, int off, 667 int size) 668 { 669 struct bpf_map *map = env->cur_state.regs[regno].map_ptr; 670 671 if (off < 0 || off + size > map->value_size) { 672 verbose("invalid access to map value, value_size=%d off=%d size=%d\n", 673 map->value_size, off, size); 674 return -EACCES; 675 } 676 return 0; 677 } 678 679 #define MAX_PACKET_OFF 0xffff 680 681 static int check_packet_access(struct verifier_env *env, u32 regno, int off, 682 int size) 683 { 684 struct reg_state *regs = env->cur_state.regs; 685 struct reg_state *reg = ®s[regno]; 686 687 off += reg->off; 688 if (off < 0 || off + size > reg->range) { 689 verbose("invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n", 690 off, size, regno, reg->id, reg->off, reg->range); 691 return -EACCES; 692 } 693 return 0; 694 } 695 696 /* check access to 'struct bpf_context' fields */ 697 static int check_ctx_access(struct verifier_env *env, int off, int size, 698 enum bpf_access_type t) 699 { 700 if (env->prog->aux->ops->is_valid_access && 701 env->prog->aux->ops->is_valid_access(off, size, t)) { 702 /* remember the offset of last byte accessed in ctx */ 703 if (env->prog->aux->max_ctx_offset < off + size) 704 env->prog->aux->max_ctx_offset = off + size; 705 return 0; 706 } 707 708 verbose("invalid bpf_context access off=%d size=%d\n", off, size); 709 return -EACCES; 710 } 711 712 static bool is_pointer_value(struct verifier_env *env, int regno) 713 { 714 if (env->allow_ptr_leaks) 715 return false; 716 717 switch (env->cur_state.regs[regno].type) { 718 case UNKNOWN_VALUE: 719 case CONST_IMM: 720 return false; 721 default: 722 return true; 723 } 724 } 725 726 static int check_ptr_alignment(struct verifier_env *env, struct reg_state *reg, 727 int off, int size) 728 { 729 if (reg->type != PTR_TO_PACKET) { 730 if (off % size != 0) { 731 verbose("misaligned access off %d size %d\n", off, size); 732 return -EACCES; 733 } else { 734 return 0; 735 } 736 } 737 738 switch (env->prog->type) { 739 case BPF_PROG_TYPE_SCHED_CLS: 740 case BPF_PROG_TYPE_SCHED_ACT: 741 break; 742 default: 743 verbose("verifier is misconfigured\n"); 744 return -EACCES; 745 } 746 747 if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) 748 /* misaligned access to packet is ok on x86,arm,arm64 */ 749 return 0; 750 751 if (reg->id && size != 1) { 752 verbose("Unknown packet alignment. Only byte-sized access allowed\n"); 753 return -EACCES; 754 } 755 756 /* skb->data is NET_IP_ALIGN-ed */ 757 if ((NET_IP_ALIGN + reg->off + off) % size != 0) { 758 verbose("misaligned packet access off %d+%d+%d size %d\n", 759 NET_IP_ALIGN, reg->off, off, size); 760 return -EACCES; 761 } 762 return 0; 763 } 764 765 /* check whether memory at (regno + off) is accessible for t = (read | write) 766 * if t==write, value_regno is a register which value is stored into memory 767 * if t==read, value_regno is a register which will receive the value from memory 768 * if t==write && value_regno==-1, some unknown value is stored into memory 769 * if t==read && value_regno==-1, don't care what we read from memory 770 */ 771 static int check_mem_access(struct verifier_env *env, u32 regno, int off, 772 int bpf_size, enum bpf_access_type t, 773 int value_regno) 774 { 775 struct verifier_state *state = &env->cur_state; 776 struct reg_state *reg = &state->regs[regno]; 777 int size, err = 0; 778 779 if (reg->type == PTR_TO_STACK) 780 off += reg->imm; 781 782 size = bpf_size_to_bytes(bpf_size); 783 if (size < 0) 784 return size; 785 786 err = check_ptr_alignment(env, reg, off, size); 787 if (err) 788 return err; 789 790 if (reg->type == PTR_TO_MAP_VALUE) { 791 if (t == BPF_WRITE && value_regno >= 0 && 792 is_pointer_value(env, value_regno)) { 793 verbose("R%d leaks addr into map\n", value_regno); 794 return -EACCES; 795 } 796 err = check_map_access(env, regno, off, size); 797 if (!err && t == BPF_READ && value_regno >= 0) 798 mark_reg_unknown_value(state->regs, value_regno); 799 800 } else if (reg->type == PTR_TO_CTX) { 801 if (t == BPF_WRITE && value_regno >= 0 && 802 is_pointer_value(env, value_regno)) { 803 verbose("R%d leaks addr into ctx\n", value_regno); 804 return -EACCES; 805 } 806 err = check_ctx_access(env, off, size, t); 807 if (!err && t == BPF_READ && value_regno >= 0) { 808 mark_reg_unknown_value(state->regs, value_regno); 809 if (off == offsetof(struct __sk_buff, data) && 810 env->allow_ptr_leaks) 811 /* note that reg.[id|off|range] == 0 */ 812 state->regs[value_regno].type = PTR_TO_PACKET; 813 else if (off == offsetof(struct __sk_buff, data_end) && 814 env->allow_ptr_leaks) 815 state->regs[value_regno].type = PTR_TO_PACKET_END; 816 } 817 818 } else if (reg->type == FRAME_PTR || reg->type == PTR_TO_STACK) { 819 if (off >= 0 || off < -MAX_BPF_STACK) { 820 verbose("invalid stack off=%d size=%d\n", off, size); 821 return -EACCES; 822 } 823 if (t == BPF_WRITE) { 824 if (!env->allow_ptr_leaks && 825 state->stack_slot_type[MAX_BPF_STACK + off] == STACK_SPILL && 826 size != BPF_REG_SIZE) { 827 verbose("attempt to corrupt spilled pointer on stack\n"); 828 return -EACCES; 829 } 830 err = check_stack_write(state, off, size, value_regno); 831 } else { 832 err = check_stack_read(state, off, size, value_regno); 833 } 834 } else if (state->regs[regno].type == PTR_TO_PACKET) { 835 if (t == BPF_WRITE) { 836 verbose("cannot write into packet\n"); 837 return -EACCES; 838 } 839 err = check_packet_access(env, regno, off, size); 840 if (!err && t == BPF_READ && value_regno >= 0) 841 mark_reg_unknown_value(state->regs, value_regno); 842 } else { 843 verbose("R%d invalid mem access '%s'\n", 844 regno, reg_type_str[reg->type]); 845 return -EACCES; 846 } 847 848 if (!err && size <= 2 && value_regno >= 0 && env->allow_ptr_leaks && 849 state->regs[value_regno].type == UNKNOWN_VALUE) { 850 /* 1 or 2 byte load zero-extends, determine the number of 851 * zero upper bits. Not doing it fo 4 byte load, since 852 * such values cannot be added to ptr_to_packet anyway. 853 */ 854 state->regs[value_regno].imm = 64 - size * 8; 855 } 856 return err; 857 } 858 859 static int check_xadd(struct verifier_env *env, struct bpf_insn *insn) 860 { 861 struct reg_state *regs = env->cur_state.regs; 862 int err; 863 864 if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) || 865 insn->imm != 0) { 866 verbose("BPF_XADD uses reserved fields\n"); 867 return -EINVAL; 868 } 869 870 /* check src1 operand */ 871 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 872 if (err) 873 return err; 874 875 /* check src2 operand */ 876 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 877 if (err) 878 return err; 879 880 /* check whether atomic_add can read the memory */ 881 err = check_mem_access(env, insn->dst_reg, insn->off, 882 BPF_SIZE(insn->code), BPF_READ, -1); 883 if (err) 884 return err; 885 886 /* check whether atomic_add can write into the same memory */ 887 return check_mem_access(env, insn->dst_reg, insn->off, 888 BPF_SIZE(insn->code), BPF_WRITE, -1); 889 } 890 891 /* when register 'regno' is passed into function that will read 'access_size' 892 * bytes from that pointer, make sure that it's within stack boundary 893 * and all elements of stack are initialized 894 */ 895 static int check_stack_boundary(struct verifier_env *env, int regno, 896 int access_size, bool zero_size_allowed, 897 struct bpf_call_arg_meta *meta) 898 { 899 struct verifier_state *state = &env->cur_state; 900 struct reg_state *regs = state->regs; 901 int off, i; 902 903 if (regs[regno].type != PTR_TO_STACK) { 904 if (zero_size_allowed && access_size == 0 && 905 regs[regno].type == CONST_IMM && 906 regs[regno].imm == 0) 907 return 0; 908 909 verbose("R%d type=%s expected=%s\n", regno, 910 reg_type_str[regs[regno].type], 911 reg_type_str[PTR_TO_STACK]); 912 return -EACCES; 913 } 914 915 off = regs[regno].imm; 916 if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 || 917 access_size <= 0) { 918 verbose("invalid stack type R%d off=%d access_size=%d\n", 919 regno, off, access_size); 920 return -EACCES; 921 } 922 923 if (meta && meta->raw_mode) { 924 meta->access_size = access_size; 925 meta->regno = regno; 926 return 0; 927 } 928 929 for (i = 0; i < access_size; i++) { 930 if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) { 931 verbose("invalid indirect read from stack off %d+%d size %d\n", 932 off, i, access_size); 933 return -EACCES; 934 } 935 } 936 return 0; 937 } 938 939 static int check_func_arg(struct verifier_env *env, u32 regno, 940 enum bpf_arg_type arg_type, 941 struct bpf_call_arg_meta *meta) 942 { 943 struct reg_state *reg = env->cur_state.regs + regno; 944 enum bpf_reg_type expected_type; 945 int err = 0; 946 947 if (arg_type == ARG_DONTCARE) 948 return 0; 949 950 if (reg->type == NOT_INIT) { 951 verbose("R%d !read_ok\n", regno); 952 return -EACCES; 953 } 954 955 if (arg_type == ARG_ANYTHING) { 956 if (is_pointer_value(env, regno)) { 957 verbose("R%d leaks addr into helper function\n", regno); 958 return -EACCES; 959 } 960 return 0; 961 } 962 963 if (arg_type == ARG_PTR_TO_MAP_KEY || 964 arg_type == ARG_PTR_TO_MAP_VALUE) { 965 expected_type = PTR_TO_STACK; 966 } else if (arg_type == ARG_CONST_STACK_SIZE || 967 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) { 968 expected_type = CONST_IMM; 969 } else if (arg_type == ARG_CONST_MAP_PTR) { 970 expected_type = CONST_PTR_TO_MAP; 971 } else if (arg_type == ARG_PTR_TO_CTX) { 972 expected_type = PTR_TO_CTX; 973 } else if (arg_type == ARG_PTR_TO_STACK || 974 arg_type == ARG_PTR_TO_RAW_STACK) { 975 expected_type = PTR_TO_STACK; 976 /* One exception here. In case function allows for NULL to be 977 * passed in as argument, it's a CONST_IMM type. Final test 978 * happens during stack boundary checking. 979 */ 980 if (reg->type == CONST_IMM && reg->imm == 0) 981 expected_type = CONST_IMM; 982 meta->raw_mode = arg_type == ARG_PTR_TO_RAW_STACK; 983 } else { 984 verbose("unsupported arg_type %d\n", arg_type); 985 return -EFAULT; 986 } 987 988 if (reg->type != expected_type) { 989 verbose("R%d type=%s expected=%s\n", regno, 990 reg_type_str[reg->type], reg_type_str[expected_type]); 991 return -EACCES; 992 } 993 994 if (arg_type == ARG_CONST_MAP_PTR) { 995 /* bpf_map_xxx(map_ptr) call: remember that map_ptr */ 996 meta->map_ptr = reg->map_ptr; 997 } else if (arg_type == ARG_PTR_TO_MAP_KEY) { 998 /* bpf_map_xxx(..., map_ptr, ..., key) call: 999 * check that [key, key + map->key_size) are within 1000 * stack limits and initialized 1001 */ 1002 if (!meta->map_ptr) { 1003 /* in function declaration map_ptr must come before 1004 * map_key, so that it's verified and known before 1005 * we have to check map_key here. Otherwise it means 1006 * that kernel subsystem misconfigured verifier 1007 */ 1008 verbose("invalid map_ptr to access map->key\n"); 1009 return -EACCES; 1010 } 1011 err = check_stack_boundary(env, regno, meta->map_ptr->key_size, 1012 false, NULL); 1013 } else if (arg_type == ARG_PTR_TO_MAP_VALUE) { 1014 /* bpf_map_xxx(..., map_ptr, ..., value) call: 1015 * check [value, value + map->value_size) validity 1016 */ 1017 if (!meta->map_ptr) { 1018 /* kernel subsystem misconfigured verifier */ 1019 verbose("invalid map_ptr to access map->value\n"); 1020 return -EACCES; 1021 } 1022 err = check_stack_boundary(env, regno, 1023 meta->map_ptr->value_size, 1024 false, NULL); 1025 } else if (arg_type == ARG_CONST_STACK_SIZE || 1026 arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) { 1027 bool zero_size_allowed = (arg_type == ARG_CONST_STACK_SIZE_OR_ZERO); 1028 1029 /* bpf_xxx(..., buf, len) call will access 'len' bytes 1030 * from stack pointer 'buf'. Check it 1031 * note: regno == len, regno - 1 == buf 1032 */ 1033 if (regno == 0) { 1034 /* kernel subsystem misconfigured verifier */ 1035 verbose("ARG_CONST_STACK_SIZE cannot be first argument\n"); 1036 return -EACCES; 1037 } 1038 err = check_stack_boundary(env, regno - 1, reg->imm, 1039 zero_size_allowed, meta); 1040 } 1041 1042 return err; 1043 } 1044 1045 static int check_map_func_compatibility(struct bpf_map *map, int func_id) 1046 { 1047 if (!map) 1048 return 0; 1049 1050 /* We need a two way check, first is from map perspective ... */ 1051 switch (map->map_type) { 1052 case BPF_MAP_TYPE_PROG_ARRAY: 1053 if (func_id != BPF_FUNC_tail_call) 1054 goto error; 1055 break; 1056 case BPF_MAP_TYPE_PERF_EVENT_ARRAY: 1057 if (func_id != BPF_FUNC_perf_event_read && 1058 func_id != BPF_FUNC_perf_event_output) 1059 goto error; 1060 break; 1061 case BPF_MAP_TYPE_STACK_TRACE: 1062 if (func_id != BPF_FUNC_get_stackid) 1063 goto error; 1064 break; 1065 default: 1066 break; 1067 } 1068 1069 /* ... and second from the function itself. */ 1070 switch (func_id) { 1071 case BPF_FUNC_tail_call: 1072 if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY) 1073 goto error; 1074 break; 1075 case BPF_FUNC_perf_event_read: 1076 case BPF_FUNC_perf_event_output: 1077 if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY) 1078 goto error; 1079 break; 1080 case BPF_FUNC_get_stackid: 1081 if (map->map_type != BPF_MAP_TYPE_STACK_TRACE) 1082 goto error; 1083 break; 1084 default: 1085 break; 1086 } 1087 1088 return 0; 1089 error: 1090 verbose("cannot pass map_type %d into func %d\n", 1091 map->map_type, func_id); 1092 return -EINVAL; 1093 } 1094 1095 static int check_raw_mode(const struct bpf_func_proto *fn) 1096 { 1097 int count = 0; 1098 1099 if (fn->arg1_type == ARG_PTR_TO_RAW_STACK) 1100 count++; 1101 if (fn->arg2_type == ARG_PTR_TO_RAW_STACK) 1102 count++; 1103 if (fn->arg3_type == ARG_PTR_TO_RAW_STACK) 1104 count++; 1105 if (fn->arg4_type == ARG_PTR_TO_RAW_STACK) 1106 count++; 1107 if (fn->arg5_type == ARG_PTR_TO_RAW_STACK) 1108 count++; 1109 1110 return count > 1 ? -EINVAL : 0; 1111 } 1112 1113 static void clear_all_pkt_pointers(struct verifier_env *env) 1114 { 1115 struct verifier_state *state = &env->cur_state; 1116 struct reg_state *regs = state->regs, *reg; 1117 int i; 1118 1119 for (i = 0; i < MAX_BPF_REG; i++) 1120 if (regs[i].type == PTR_TO_PACKET || 1121 regs[i].type == PTR_TO_PACKET_END) 1122 mark_reg_unknown_value(regs, i); 1123 1124 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 1125 if (state->stack_slot_type[i] != STACK_SPILL) 1126 continue; 1127 reg = &state->spilled_regs[i / BPF_REG_SIZE]; 1128 if (reg->type != PTR_TO_PACKET && 1129 reg->type != PTR_TO_PACKET_END) 1130 continue; 1131 reg->type = UNKNOWN_VALUE; 1132 reg->imm = 0; 1133 } 1134 } 1135 1136 static int check_call(struct verifier_env *env, int func_id) 1137 { 1138 struct verifier_state *state = &env->cur_state; 1139 const struct bpf_func_proto *fn = NULL; 1140 struct reg_state *regs = state->regs; 1141 struct reg_state *reg; 1142 struct bpf_call_arg_meta meta; 1143 bool changes_data; 1144 int i, err; 1145 1146 /* find function prototype */ 1147 if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) { 1148 verbose("invalid func %d\n", func_id); 1149 return -EINVAL; 1150 } 1151 1152 if (env->prog->aux->ops->get_func_proto) 1153 fn = env->prog->aux->ops->get_func_proto(func_id); 1154 1155 if (!fn) { 1156 verbose("unknown func %d\n", func_id); 1157 return -EINVAL; 1158 } 1159 1160 /* eBPF programs must be GPL compatible to use GPL-ed functions */ 1161 if (!env->prog->gpl_compatible && fn->gpl_only) { 1162 verbose("cannot call GPL only function from proprietary program\n"); 1163 return -EINVAL; 1164 } 1165 1166 changes_data = bpf_helper_changes_skb_data(fn->func); 1167 1168 memset(&meta, 0, sizeof(meta)); 1169 1170 /* We only support one arg being in raw mode at the moment, which 1171 * is sufficient for the helper functions we have right now. 1172 */ 1173 err = check_raw_mode(fn); 1174 if (err) { 1175 verbose("kernel subsystem misconfigured func %d\n", func_id); 1176 return err; 1177 } 1178 1179 /* check args */ 1180 err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta); 1181 if (err) 1182 return err; 1183 err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta); 1184 if (err) 1185 return err; 1186 err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta); 1187 if (err) 1188 return err; 1189 err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &meta); 1190 if (err) 1191 return err; 1192 err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &meta); 1193 if (err) 1194 return err; 1195 1196 /* Mark slots with STACK_MISC in case of raw mode, stack offset 1197 * is inferred from register state. 1198 */ 1199 for (i = 0; i < meta.access_size; i++) { 1200 err = check_mem_access(env, meta.regno, i, BPF_B, BPF_WRITE, -1); 1201 if (err) 1202 return err; 1203 } 1204 1205 /* reset caller saved regs */ 1206 for (i = 0; i < CALLER_SAVED_REGS; i++) { 1207 reg = regs + caller_saved[i]; 1208 reg->type = NOT_INIT; 1209 reg->imm = 0; 1210 } 1211 1212 /* update return register */ 1213 if (fn->ret_type == RET_INTEGER) { 1214 regs[BPF_REG_0].type = UNKNOWN_VALUE; 1215 } else if (fn->ret_type == RET_VOID) { 1216 regs[BPF_REG_0].type = NOT_INIT; 1217 } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) { 1218 regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL; 1219 /* remember map_ptr, so that check_map_access() 1220 * can check 'value_size' boundary of memory access 1221 * to map element returned from bpf_map_lookup_elem() 1222 */ 1223 if (meta.map_ptr == NULL) { 1224 verbose("kernel subsystem misconfigured verifier\n"); 1225 return -EINVAL; 1226 } 1227 regs[BPF_REG_0].map_ptr = meta.map_ptr; 1228 } else { 1229 verbose("unknown return type %d of func %d\n", 1230 fn->ret_type, func_id); 1231 return -EINVAL; 1232 } 1233 1234 err = check_map_func_compatibility(meta.map_ptr, func_id); 1235 if (err) 1236 return err; 1237 1238 if (changes_data) 1239 clear_all_pkt_pointers(env); 1240 return 0; 1241 } 1242 1243 static int check_packet_ptr_add(struct verifier_env *env, struct bpf_insn *insn) 1244 { 1245 struct reg_state *regs = env->cur_state.regs; 1246 struct reg_state *dst_reg = ®s[insn->dst_reg]; 1247 struct reg_state *src_reg = ®s[insn->src_reg]; 1248 struct reg_state tmp_reg; 1249 s32 imm; 1250 1251 if (BPF_SRC(insn->code) == BPF_K) { 1252 /* pkt_ptr += imm */ 1253 imm = insn->imm; 1254 1255 add_imm: 1256 if (imm <= 0) { 1257 verbose("addition of negative constant to packet pointer is not allowed\n"); 1258 return -EACCES; 1259 } 1260 if (imm >= MAX_PACKET_OFF || 1261 imm + dst_reg->off >= MAX_PACKET_OFF) { 1262 verbose("constant %d is too large to add to packet pointer\n", 1263 imm); 1264 return -EACCES; 1265 } 1266 /* a constant was added to pkt_ptr. 1267 * Remember it while keeping the same 'id' 1268 */ 1269 dst_reg->off += imm; 1270 } else { 1271 if (src_reg->type == PTR_TO_PACKET) { 1272 /* R6=pkt(id=0,off=0,r=62) R7=imm22; r7 += r6 */ 1273 tmp_reg = *dst_reg; /* save r7 state */ 1274 *dst_reg = *src_reg; /* copy pkt_ptr state r6 into r7 */ 1275 src_reg = &tmp_reg; /* pretend it's src_reg state */ 1276 /* if the checks below reject it, the copy won't matter, 1277 * since we're rejecting the whole program. If all ok, 1278 * then imm22 state will be added to r7 1279 * and r7 will be pkt(id=0,off=22,r=62) while 1280 * r6 will stay as pkt(id=0,off=0,r=62) 1281 */ 1282 } 1283 1284 if (src_reg->type == CONST_IMM) { 1285 /* pkt_ptr += reg where reg is known constant */ 1286 imm = src_reg->imm; 1287 goto add_imm; 1288 } 1289 /* disallow pkt_ptr += reg 1290 * if reg is not uknown_value with guaranteed zero upper bits 1291 * otherwise pkt_ptr may overflow and addition will become 1292 * subtraction which is not allowed 1293 */ 1294 if (src_reg->type != UNKNOWN_VALUE) { 1295 verbose("cannot add '%s' to ptr_to_packet\n", 1296 reg_type_str[src_reg->type]); 1297 return -EACCES; 1298 } 1299 if (src_reg->imm < 48) { 1300 verbose("cannot add integer value with %lld upper zero bits to ptr_to_packet\n", 1301 src_reg->imm); 1302 return -EACCES; 1303 } 1304 /* dst_reg stays as pkt_ptr type and since some positive 1305 * integer value was added to the pointer, increment its 'id' 1306 */ 1307 dst_reg->id++; 1308 1309 /* something was added to pkt_ptr, set range and off to zero */ 1310 dst_reg->off = 0; 1311 dst_reg->range = 0; 1312 } 1313 return 0; 1314 } 1315 1316 static int evaluate_reg_alu(struct verifier_env *env, struct bpf_insn *insn) 1317 { 1318 struct reg_state *regs = env->cur_state.regs; 1319 struct reg_state *dst_reg = ®s[insn->dst_reg]; 1320 u8 opcode = BPF_OP(insn->code); 1321 s64 imm_log2; 1322 1323 /* for type == UNKNOWN_VALUE: 1324 * imm > 0 -> number of zero upper bits 1325 * imm == 0 -> don't track which is the same as all bits can be non-zero 1326 */ 1327 1328 if (BPF_SRC(insn->code) == BPF_X) { 1329 struct reg_state *src_reg = ®s[insn->src_reg]; 1330 1331 if (src_reg->type == UNKNOWN_VALUE && src_reg->imm > 0 && 1332 dst_reg->imm && opcode == BPF_ADD) { 1333 /* dreg += sreg 1334 * where both have zero upper bits. Adding them 1335 * can only result making one more bit non-zero 1336 * in the larger value. 1337 * Ex. 0xffff (imm=48) + 1 (imm=63) = 0x10000 (imm=47) 1338 * 0xffff (imm=48) + 0xffff = 0x1fffe (imm=47) 1339 */ 1340 dst_reg->imm = min(dst_reg->imm, src_reg->imm); 1341 dst_reg->imm--; 1342 return 0; 1343 } 1344 if (src_reg->type == CONST_IMM && src_reg->imm > 0 && 1345 dst_reg->imm && opcode == BPF_ADD) { 1346 /* dreg += sreg 1347 * where dreg has zero upper bits and sreg is const. 1348 * Adding them can only result making one more bit 1349 * non-zero in the larger value. 1350 */ 1351 imm_log2 = __ilog2_u64((long long)src_reg->imm); 1352 dst_reg->imm = min(dst_reg->imm, 63 - imm_log2); 1353 dst_reg->imm--; 1354 return 0; 1355 } 1356 /* all other cases non supported yet, just mark dst_reg */ 1357 dst_reg->imm = 0; 1358 return 0; 1359 } 1360 1361 /* sign extend 32-bit imm into 64-bit to make sure that 1362 * negative values occupy bit 63. Note ilog2() would have 1363 * been incorrect, since sizeof(insn->imm) == 4 1364 */ 1365 imm_log2 = __ilog2_u64((long long)insn->imm); 1366 1367 if (dst_reg->imm && opcode == BPF_LSH) { 1368 /* reg <<= imm 1369 * if reg was a result of 2 byte load, then its imm == 48 1370 * which means that upper 48 bits are zero and shifting this reg 1371 * left by 4 would mean that upper 44 bits are still zero 1372 */ 1373 dst_reg->imm -= insn->imm; 1374 } else if (dst_reg->imm && opcode == BPF_MUL) { 1375 /* reg *= imm 1376 * if multiplying by 14 subtract 4 1377 * This is conservative calculation of upper zero bits. 1378 * It's not trying to special case insn->imm == 1 or 0 cases 1379 */ 1380 dst_reg->imm -= imm_log2 + 1; 1381 } else if (opcode == BPF_AND) { 1382 /* reg &= imm */ 1383 dst_reg->imm = 63 - imm_log2; 1384 } else if (dst_reg->imm && opcode == BPF_ADD) { 1385 /* reg += imm */ 1386 dst_reg->imm = min(dst_reg->imm, 63 - imm_log2); 1387 dst_reg->imm--; 1388 } else if (opcode == BPF_RSH) { 1389 /* reg >>= imm 1390 * which means that after right shift, upper bits will be zero 1391 * note that verifier already checked that 1392 * 0 <= imm < 64 for shift insn 1393 */ 1394 dst_reg->imm += insn->imm; 1395 if (unlikely(dst_reg->imm > 64)) 1396 /* some dumb code did: 1397 * r2 = *(u32 *)mem; 1398 * r2 >>= 32; 1399 * and all bits are zero now */ 1400 dst_reg->imm = 64; 1401 } else { 1402 /* all other alu ops, means that we don't know what will 1403 * happen to the value, mark it with unknown number of zero bits 1404 */ 1405 dst_reg->imm = 0; 1406 } 1407 1408 if (dst_reg->imm < 0) { 1409 /* all 64 bits of the register can contain non-zero bits 1410 * and such value cannot be added to ptr_to_packet, since it 1411 * may overflow, mark it as unknown to avoid further eval 1412 */ 1413 dst_reg->imm = 0; 1414 } 1415 return 0; 1416 } 1417 1418 static int evaluate_reg_imm_alu(struct verifier_env *env, struct bpf_insn *insn) 1419 { 1420 struct reg_state *regs = env->cur_state.regs; 1421 struct reg_state *dst_reg = ®s[insn->dst_reg]; 1422 struct reg_state *src_reg = ®s[insn->src_reg]; 1423 u8 opcode = BPF_OP(insn->code); 1424 1425 /* dst_reg->type == CONST_IMM here, simulate execution of 'add' insn. 1426 * Don't care about overflow or negative values, just add them 1427 */ 1428 if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_K) 1429 dst_reg->imm += insn->imm; 1430 else if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_X && 1431 src_reg->type == CONST_IMM) 1432 dst_reg->imm += src_reg->imm; 1433 else 1434 mark_reg_unknown_value(regs, insn->dst_reg); 1435 return 0; 1436 } 1437 1438 /* check validity of 32-bit and 64-bit arithmetic operations */ 1439 static int check_alu_op(struct verifier_env *env, struct bpf_insn *insn) 1440 { 1441 struct reg_state *regs = env->cur_state.regs, *dst_reg; 1442 u8 opcode = BPF_OP(insn->code); 1443 int err; 1444 1445 if (opcode == BPF_END || opcode == BPF_NEG) { 1446 if (opcode == BPF_NEG) { 1447 if (BPF_SRC(insn->code) != 0 || 1448 insn->src_reg != BPF_REG_0 || 1449 insn->off != 0 || insn->imm != 0) { 1450 verbose("BPF_NEG uses reserved fields\n"); 1451 return -EINVAL; 1452 } 1453 } else { 1454 if (insn->src_reg != BPF_REG_0 || insn->off != 0 || 1455 (insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) { 1456 verbose("BPF_END uses reserved fields\n"); 1457 return -EINVAL; 1458 } 1459 } 1460 1461 /* check src operand */ 1462 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1463 if (err) 1464 return err; 1465 1466 if (is_pointer_value(env, insn->dst_reg)) { 1467 verbose("R%d pointer arithmetic prohibited\n", 1468 insn->dst_reg); 1469 return -EACCES; 1470 } 1471 1472 /* check dest operand */ 1473 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1474 if (err) 1475 return err; 1476 1477 } else if (opcode == BPF_MOV) { 1478 1479 if (BPF_SRC(insn->code) == BPF_X) { 1480 if (insn->imm != 0 || insn->off != 0) { 1481 verbose("BPF_MOV uses reserved fields\n"); 1482 return -EINVAL; 1483 } 1484 1485 /* check src operand */ 1486 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1487 if (err) 1488 return err; 1489 } else { 1490 if (insn->src_reg != BPF_REG_0 || insn->off != 0) { 1491 verbose("BPF_MOV uses reserved fields\n"); 1492 return -EINVAL; 1493 } 1494 } 1495 1496 /* check dest operand */ 1497 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1498 if (err) 1499 return err; 1500 1501 if (BPF_SRC(insn->code) == BPF_X) { 1502 if (BPF_CLASS(insn->code) == BPF_ALU64) { 1503 /* case: R1 = R2 1504 * copy register state to dest reg 1505 */ 1506 regs[insn->dst_reg] = regs[insn->src_reg]; 1507 } else { 1508 if (is_pointer_value(env, insn->src_reg)) { 1509 verbose("R%d partial copy of pointer\n", 1510 insn->src_reg); 1511 return -EACCES; 1512 } 1513 regs[insn->dst_reg].type = UNKNOWN_VALUE; 1514 regs[insn->dst_reg].map_ptr = NULL; 1515 } 1516 } else { 1517 /* case: R = imm 1518 * remember the value we stored into this reg 1519 */ 1520 regs[insn->dst_reg].type = CONST_IMM; 1521 regs[insn->dst_reg].imm = insn->imm; 1522 } 1523 1524 } else if (opcode > BPF_END) { 1525 verbose("invalid BPF_ALU opcode %x\n", opcode); 1526 return -EINVAL; 1527 1528 } else { /* all other ALU ops: and, sub, xor, add, ... */ 1529 1530 if (BPF_SRC(insn->code) == BPF_X) { 1531 if (insn->imm != 0 || insn->off != 0) { 1532 verbose("BPF_ALU uses reserved fields\n"); 1533 return -EINVAL; 1534 } 1535 /* check src1 operand */ 1536 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1537 if (err) 1538 return err; 1539 } else { 1540 if (insn->src_reg != BPF_REG_0 || insn->off != 0) { 1541 verbose("BPF_ALU uses reserved fields\n"); 1542 return -EINVAL; 1543 } 1544 } 1545 1546 /* check src2 operand */ 1547 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1548 if (err) 1549 return err; 1550 1551 if ((opcode == BPF_MOD || opcode == BPF_DIV) && 1552 BPF_SRC(insn->code) == BPF_K && insn->imm == 0) { 1553 verbose("div by zero\n"); 1554 return -EINVAL; 1555 } 1556 1557 if ((opcode == BPF_LSH || opcode == BPF_RSH || 1558 opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) { 1559 int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32; 1560 1561 if (insn->imm < 0 || insn->imm >= size) { 1562 verbose("invalid shift %d\n", insn->imm); 1563 return -EINVAL; 1564 } 1565 } 1566 1567 /* check dest operand */ 1568 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK); 1569 if (err) 1570 return err; 1571 1572 dst_reg = ®s[insn->dst_reg]; 1573 1574 /* pattern match 'bpf_add Rx, imm' instruction */ 1575 if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 && 1576 dst_reg->type == FRAME_PTR && BPF_SRC(insn->code) == BPF_K) { 1577 dst_reg->type = PTR_TO_STACK; 1578 dst_reg->imm = insn->imm; 1579 return 0; 1580 } else if (opcode == BPF_ADD && 1581 BPF_CLASS(insn->code) == BPF_ALU64 && 1582 (dst_reg->type == PTR_TO_PACKET || 1583 (BPF_SRC(insn->code) == BPF_X && 1584 regs[insn->src_reg].type == PTR_TO_PACKET))) { 1585 /* ptr_to_packet += K|X */ 1586 return check_packet_ptr_add(env, insn); 1587 } else if (BPF_CLASS(insn->code) == BPF_ALU64 && 1588 dst_reg->type == UNKNOWN_VALUE && 1589 env->allow_ptr_leaks) { 1590 /* unknown += K|X */ 1591 return evaluate_reg_alu(env, insn); 1592 } else if (BPF_CLASS(insn->code) == BPF_ALU64 && 1593 dst_reg->type == CONST_IMM && 1594 env->allow_ptr_leaks) { 1595 /* reg_imm += K|X */ 1596 return evaluate_reg_imm_alu(env, insn); 1597 } else if (is_pointer_value(env, insn->dst_reg)) { 1598 verbose("R%d pointer arithmetic prohibited\n", 1599 insn->dst_reg); 1600 return -EACCES; 1601 } else if (BPF_SRC(insn->code) == BPF_X && 1602 is_pointer_value(env, insn->src_reg)) { 1603 verbose("R%d pointer arithmetic prohibited\n", 1604 insn->src_reg); 1605 return -EACCES; 1606 } 1607 1608 /* mark dest operand */ 1609 mark_reg_unknown_value(regs, insn->dst_reg); 1610 } 1611 1612 return 0; 1613 } 1614 1615 static void find_good_pkt_pointers(struct verifier_env *env, 1616 struct reg_state *dst_reg) 1617 { 1618 struct verifier_state *state = &env->cur_state; 1619 struct reg_state *regs = state->regs, *reg; 1620 int i; 1621 /* r2 = r3; 1622 * r2 += 8 1623 * if (r2 > pkt_end) goto somewhere 1624 * r2 == dst_reg, pkt_end == src_reg, 1625 * r2=pkt(id=n,off=8,r=0) 1626 * r3=pkt(id=n,off=0,r=0) 1627 * find register r3 and mark its range as r3=pkt(id=n,off=0,r=8) 1628 * so that range of bytes [r3, r3 + 8) is safe to access 1629 */ 1630 for (i = 0; i < MAX_BPF_REG; i++) 1631 if (regs[i].type == PTR_TO_PACKET && regs[i].id == dst_reg->id) 1632 regs[i].range = dst_reg->off; 1633 1634 for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { 1635 if (state->stack_slot_type[i] != STACK_SPILL) 1636 continue; 1637 reg = &state->spilled_regs[i / BPF_REG_SIZE]; 1638 if (reg->type == PTR_TO_PACKET && reg->id == dst_reg->id) 1639 reg->range = dst_reg->off; 1640 } 1641 } 1642 1643 static int check_cond_jmp_op(struct verifier_env *env, 1644 struct bpf_insn *insn, int *insn_idx) 1645 { 1646 struct reg_state *regs = env->cur_state.regs, *dst_reg; 1647 struct verifier_state *other_branch; 1648 u8 opcode = BPF_OP(insn->code); 1649 int err; 1650 1651 if (opcode > BPF_EXIT) { 1652 verbose("invalid BPF_JMP opcode %x\n", opcode); 1653 return -EINVAL; 1654 } 1655 1656 if (BPF_SRC(insn->code) == BPF_X) { 1657 if (insn->imm != 0) { 1658 verbose("BPF_JMP uses reserved fields\n"); 1659 return -EINVAL; 1660 } 1661 1662 /* check src1 operand */ 1663 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1664 if (err) 1665 return err; 1666 1667 if (is_pointer_value(env, insn->src_reg)) { 1668 verbose("R%d pointer comparison prohibited\n", 1669 insn->src_reg); 1670 return -EACCES; 1671 } 1672 } else { 1673 if (insn->src_reg != BPF_REG_0) { 1674 verbose("BPF_JMP uses reserved fields\n"); 1675 return -EINVAL; 1676 } 1677 } 1678 1679 /* check src2 operand */ 1680 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 1681 if (err) 1682 return err; 1683 1684 dst_reg = ®s[insn->dst_reg]; 1685 1686 /* detect if R == 0 where R was initialized to zero earlier */ 1687 if (BPF_SRC(insn->code) == BPF_K && 1688 (opcode == BPF_JEQ || opcode == BPF_JNE) && 1689 dst_reg->type == CONST_IMM && dst_reg->imm == insn->imm) { 1690 if (opcode == BPF_JEQ) { 1691 /* if (imm == imm) goto pc+off; 1692 * only follow the goto, ignore fall-through 1693 */ 1694 *insn_idx += insn->off; 1695 return 0; 1696 } else { 1697 /* if (imm != imm) goto pc+off; 1698 * only follow fall-through branch, since 1699 * that's where the program will go 1700 */ 1701 return 0; 1702 } 1703 } 1704 1705 other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx); 1706 if (!other_branch) 1707 return -EFAULT; 1708 1709 /* detect if R == 0 where R is returned value from bpf_map_lookup_elem() */ 1710 if (BPF_SRC(insn->code) == BPF_K && 1711 insn->imm == 0 && (opcode == BPF_JEQ || opcode == BPF_JNE) && 1712 dst_reg->type == PTR_TO_MAP_VALUE_OR_NULL) { 1713 if (opcode == BPF_JEQ) { 1714 /* next fallthrough insn can access memory via 1715 * this register 1716 */ 1717 regs[insn->dst_reg].type = PTR_TO_MAP_VALUE; 1718 /* branch targer cannot access it, since reg == 0 */ 1719 mark_reg_unknown_value(other_branch->regs, 1720 insn->dst_reg); 1721 } else { 1722 other_branch->regs[insn->dst_reg].type = PTR_TO_MAP_VALUE; 1723 mark_reg_unknown_value(regs, insn->dst_reg); 1724 } 1725 } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT && 1726 dst_reg->type == PTR_TO_PACKET && 1727 regs[insn->src_reg].type == PTR_TO_PACKET_END) { 1728 find_good_pkt_pointers(env, dst_reg); 1729 } else if (is_pointer_value(env, insn->dst_reg)) { 1730 verbose("R%d pointer comparison prohibited\n", insn->dst_reg); 1731 return -EACCES; 1732 } 1733 if (log_level) 1734 print_verifier_state(&env->cur_state); 1735 return 0; 1736 } 1737 1738 /* return the map pointer stored inside BPF_LD_IMM64 instruction */ 1739 static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn) 1740 { 1741 u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32; 1742 1743 return (struct bpf_map *) (unsigned long) imm64; 1744 } 1745 1746 /* verify BPF_LD_IMM64 instruction */ 1747 static int check_ld_imm(struct verifier_env *env, struct bpf_insn *insn) 1748 { 1749 struct reg_state *regs = env->cur_state.regs; 1750 int err; 1751 1752 if (BPF_SIZE(insn->code) != BPF_DW) { 1753 verbose("invalid BPF_LD_IMM insn\n"); 1754 return -EINVAL; 1755 } 1756 if (insn->off != 0) { 1757 verbose("BPF_LD_IMM64 uses reserved fields\n"); 1758 return -EINVAL; 1759 } 1760 1761 err = check_reg_arg(regs, insn->dst_reg, DST_OP); 1762 if (err) 1763 return err; 1764 1765 if (insn->src_reg == 0) 1766 /* generic move 64-bit immediate into a register */ 1767 return 0; 1768 1769 /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */ 1770 BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD); 1771 1772 regs[insn->dst_reg].type = CONST_PTR_TO_MAP; 1773 regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn); 1774 return 0; 1775 } 1776 1777 static bool may_access_skb(enum bpf_prog_type type) 1778 { 1779 switch (type) { 1780 case BPF_PROG_TYPE_SOCKET_FILTER: 1781 case BPF_PROG_TYPE_SCHED_CLS: 1782 case BPF_PROG_TYPE_SCHED_ACT: 1783 return true; 1784 default: 1785 return false; 1786 } 1787 } 1788 1789 /* verify safety of LD_ABS|LD_IND instructions: 1790 * - they can only appear in the programs where ctx == skb 1791 * - since they are wrappers of function calls, they scratch R1-R5 registers, 1792 * preserve R6-R9, and store return value into R0 1793 * 1794 * Implicit input: 1795 * ctx == skb == R6 == CTX 1796 * 1797 * Explicit input: 1798 * SRC == any register 1799 * IMM == 32-bit immediate 1800 * 1801 * Output: 1802 * R0 - 8/16/32-bit skb data converted to cpu endianness 1803 */ 1804 static int check_ld_abs(struct verifier_env *env, struct bpf_insn *insn) 1805 { 1806 struct reg_state *regs = env->cur_state.regs; 1807 u8 mode = BPF_MODE(insn->code); 1808 struct reg_state *reg; 1809 int i, err; 1810 1811 if (!may_access_skb(env->prog->type)) { 1812 verbose("BPF_LD_[ABS|IND] instructions not allowed for this program type\n"); 1813 return -EINVAL; 1814 } 1815 1816 if (insn->dst_reg != BPF_REG_0 || insn->off != 0 || 1817 BPF_SIZE(insn->code) == BPF_DW || 1818 (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) { 1819 verbose("BPF_LD_[ABS|IND] uses reserved fields\n"); 1820 return -EINVAL; 1821 } 1822 1823 /* check whether implicit source operand (register R6) is readable */ 1824 err = check_reg_arg(regs, BPF_REG_6, SRC_OP); 1825 if (err) 1826 return err; 1827 1828 if (regs[BPF_REG_6].type != PTR_TO_CTX) { 1829 verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n"); 1830 return -EINVAL; 1831 } 1832 1833 if (mode == BPF_IND) { 1834 /* check explicit source operand */ 1835 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 1836 if (err) 1837 return err; 1838 } 1839 1840 /* reset caller saved regs to unreadable */ 1841 for (i = 0; i < CALLER_SAVED_REGS; i++) { 1842 reg = regs + caller_saved[i]; 1843 reg->type = NOT_INIT; 1844 reg->imm = 0; 1845 } 1846 1847 /* mark destination R0 register as readable, since it contains 1848 * the value fetched from the packet 1849 */ 1850 regs[BPF_REG_0].type = UNKNOWN_VALUE; 1851 return 0; 1852 } 1853 1854 /* non-recursive DFS pseudo code 1855 * 1 procedure DFS-iterative(G,v): 1856 * 2 label v as discovered 1857 * 3 let S be a stack 1858 * 4 S.push(v) 1859 * 5 while S is not empty 1860 * 6 t <- S.pop() 1861 * 7 if t is what we're looking for: 1862 * 8 return t 1863 * 9 for all edges e in G.adjacentEdges(t) do 1864 * 10 if edge e is already labelled 1865 * 11 continue with the next edge 1866 * 12 w <- G.adjacentVertex(t,e) 1867 * 13 if vertex w is not discovered and not explored 1868 * 14 label e as tree-edge 1869 * 15 label w as discovered 1870 * 16 S.push(w) 1871 * 17 continue at 5 1872 * 18 else if vertex w is discovered 1873 * 19 label e as back-edge 1874 * 20 else 1875 * 21 // vertex w is explored 1876 * 22 label e as forward- or cross-edge 1877 * 23 label t as explored 1878 * 24 S.pop() 1879 * 1880 * convention: 1881 * 0x10 - discovered 1882 * 0x11 - discovered and fall-through edge labelled 1883 * 0x12 - discovered and fall-through and branch edges labelled 1884 * 0x20 - explored 1885 */ 1886 1887 enum { 1888 DISCOVERED = 0x10, 1889 EXPLORED = 0x20, 1890 FALLTHROUGH = 1, 1891 BRANCH = 2, 1892 }; 1893 1894 #define STATE_LIST_MARK ((struct verifier_state_list *) -1L) 1895 1896 static int *insn_stack; /* stack of insns to process */ 1897 static int cur_stack; /* current stack index */ 1898 static int *insn_state; 1899 1900 /* t, w, e - match pseudo-code above: 1901 * t - index of current instruction 1902 * w - next instruction 1903 * e - edge 1904 */ 1905 static int push_insn(int t, int w, int e, struct verifier_env *env) 1906 { 1907 if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH)) 1908 return 0; 1909 1910 if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH)) 1911 return 0; 1912 1913 if (w < 0 || w >= env->prog->len) { 1914 verbose("jump out of range from insn %d to %d\n", t, w); 1915 return -EINVAL; 1916 } 1917 1918 if (e == BRANCH) 1919 /* mark branch target for state pruning */ 1920 env->explored_states[w] = STATE_LIST_MARK; 1921 1922 if (insn_state[w] == 0) { 1923 /* tree-edge */ 1924 insn_state[t] = DISCOVERED | e; 1925 insn_state[w] = DISCOVERED; 1926 if (cur_stack >= env->prog->len) 1927 return -E2BIG; 1928 insn_stack[cur_stack++] = w; 1929 return 1; 1930 } else if ((insn_state[w] & 0xF0) == DISCOVERED) { 1931 verbose("back-edge from insn %d to %d\n", t, w); 1932 return -EINVAL; 1933 } else if (insn_state[w] == EXPLORED) { 1934 /* forward- or cross-edge */ 1935 insn_state[t] = DISCOVERED | e; 1936 } else { 1937 verbose("insn state internal bug\n"); 1938 return -EFAULT; 1939 } 1940 return 0; 1941 } 1942 1943 /* non-recursive depth-first-search to detect loops in BPF program 1944 * loop == back-edge in directed graph 1945 */ 1946 static int check_cfg(struct verifier_env *env) 1947 { 1948 struct bpf_insn *insns = env->prog->insnsi; 1949 int insn_cnt = env->prog->len; 1950 int ret = 0; 1951 int i, t; 1952 1953 insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); 1954 if (!insn_state) 1955 return -ENOMEM; 1956 1957 insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); 1958 if (!insn_stack) { 1959 kfree(insn_state); 1960 return -ENOMEM; 1961 } 1962 1963 insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */ 1964 insn_stack[0] = 0; /* 0 is the first instruction */ 1965 cur_stack = 1; 1966 1967 peek_stack: 1968 if (cur_stack == 0) 1969 goto check_state; 1970 t = insn_stack[cur_stack - 1]; 1971 1972 if (BPF_CLASS(insns[t].code) == BPF_JMP) { 1973 u8 opcode = BPF_OP(insns[t].code); 1974 1975 if (opcode == BPF_EXIT) { 1976 goto mark_explored; 1977 } else if (opcode == BPF_CALL) { 1978 ret = push_insn(t, t + 1, FALLTHROUGH, env); 1979 if (ret == 1) 1980 goto peek_stack; 1981 else if (ret < 0) 1982 goto err_free; 1983 if (t + 1 < insn_cnt) 1984 env->explored_states[t + 1] = STATE_LIST_MARK; 1985 } else if (opcode == BPF_JA) { 1986 if (BPF_SRC(insns[t].code) != BPF_K) { 1987 ret = -EINVAL; 1988 goto err_free; 1989 } 1990 /* unconditional jump with single edge */ 1991 ret = push_insn(t, t + insns[t].off + 1, 1992 FALLTHROUGH, env); 1993 if (ret == 1) 1994 goto peek_stack; 1995 else if (ret < 0) 1996 goto err_free; 1997 /* tell verifier to check for equivalent states 1998 * after every call and jump 1999 */ 2000 if (t + 1 < insn_cnt) 2001 env->explored_states[t + 1] = STATE_LIST_MARK; 2002 } else { 2003 /* conditional jump with two edges */ 2004 ret = push_insn(t, t + 1, FALLTHROUGH, env); 2005 if (ret == 1) 2006 goto peek_stack; 2007 else if (ret < 0) 2008 goto err_free; 2009 2010 ret = push_insn(t, t + insns[t].off + 1, BRANCH, env); 2011 if (ret == 1) 2012 goto peek_stack; 2013 else if (ret < 0) 2014 goto err_free; 2015 } 2016 } else { 2017 /* all other non-branch instructions with single 2018 * fall-through edge 2019 */ 2020 ret = push_insn(t, t + 1, FALLTHROUGH, env); 2021 if (ret == 1) 2022 goto peek_stack; 2023 else if (ret < 0) 2024 goto err_free; 2025 } 2026 2027 mark_explored: 2028 insn_state[t] = EXPLORED; 2029 if (cur_stack-- <= 0) { 2030 verbose("pop stack internal bug\n"); 2031 ret = -EFAULT; 2032 goto err_free; 2033 } 2034 goto peek_stack; 2035 2036 check_state: 2037 for (i = 0; i < insn_cnt; i++) { 2038 if (insn_state[i] != EXPLORED) { 2039 verbose("unreachable insn %d\n", i); 2040 ret = -EINVAL; 2041 goto err_free; 2042 } 2043 } 2044 ret = 0; /* cfg looks good */ 2045 2046 err_free: 2047 kfree(insn_state); 2048 kfree(insn_stack); 2049 return ret; 2050 } 2051 2052 /* the following conditions reduce the number of explored insns 2053 * from ~140k to ~80k for ultra large programs that use a lot of ptr_to_packet 2054 */ 2055 static bool compare_ptrs_to_packet(struct reg_state *old, struct reg_state *cur) 2056 { 2057 if (old->id != cur->id) 2058 return false; 2059 2060 /* old ptr_to_packet is more conservative, since it allows smaller 2061 * range. Ex: 2062 * old(off=0,r=10) is equal to cur(off=0,r=20), because 2063 * old(off=0,r=10) means that with range=10 the verifier proceeded 2064 * further and found no issues with the program. Now we're in the same 2065 * spot with cur(off=0,r=20), so we're safe too, since anything further 2066 * will only be looking at most 10 bytes after this pointer. 2067 */ 2068 if (old->off == cur->off && old->range < cur->range) 2069 return true; 2070 2071 /* old(off=20,r=10) is equal to cur(off=22,re=22 or 5 or 0) 2072 * since both cannot be used for packet access and safe(old) 2073 * pointer has smaller off that could be used for further 2074 * 'if (ptr > data_end)' check 2075 * Ex: 2076 * old(off=20,r=10) and cur(off=22,r=22) and cur(off=22,r=0) mean 2077 * that we cannot access the packet. 2078 * The safe range is: 2079 * [ptr, ptr + range - off) 2080 * so whenever off >=range, it means no safe bytes from this pointer. 2081 * When comparing old->off <= cur->off, it means that older code 2082 * went with smaller offset and that offset was later 2083 * used to figure out the safe range after 'if (ptr > data_end)' check 2084 * Say, 'old' state was explored like: 2085 * ... R3(off=0, r=0) 2086 * R4 = R3 + 20 2087 * ... now R4(off=20,r=0) <-- here 2088 * if (R4 > data_end) 2089 * ... R4(off=20,r=20), R3(off=0,r=20) and R3 can be used to access. 2090 * ... the code further went all the way to bpf_exit. 2091 * Now the 'cur' state at the mark 'here' has R4(off=30,r=0). 2092 * old_R4(off=20,r=0) equal to cur_R4(off=30,r=0), since if the verifier 2093 * goes further, such cur_R4 will give larger safe packet range after 2094 * 'if (R4 > data_end)' and all further insn were already good with r=20, 2095 * so they will be good with r=30 and we can prune the search. 2096 */ 2097 if (old->off <= cur->off && 2098 old->off >= old->range && cur->off >= cur->range) 2099 return true; 2100 2101 return false; 2102 } 2103 2104 /* compare two verifier states 2105 * 2106 * all states stored in state_list are known to be valid, since 2107 * verifier reached 'bpf_exit' instruction through them 2108 * 2109 * this function is called when verifier exploring different branches of 2110 * execution popped from the state stack. If it sees an old state that has 2111 * more strict register state and more strict stack state then this execution 2112 * branch doesn't need to be explored further, since verifier already 2113 * concluded that more strict state leads to valid finish. 2114 * 2115 * Therefore two states are equivalent if register state is more conservative 2116 * and explored stack state is more conservative than the current one. 2117 * Example: 2118 * explored current 2119 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC) 2120 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC) 2121 * 2122 * In other words if current stack state (one being explored) has more 2123 * valid slots than old one that already passed validation, it means 2124 * the verifier can stop exploring and conclude that current state is valid too 2125 * 2126 * Similarly with registers. If explored state has register type as invalid 2127 * whereas register type in current state is meaningful, it means that 2128 * the current state will reach 'bpf_exit' instruction safely 2129 */ 2130 static bool states_equal(struct verifier_state *old, struct verifier_state *cur) 2131 { 2132 struct reg_state *rold, *rcur; 2133 int i; 2134 2135 for (i = 0; i < MAX_BPF_REG; i++) { 2136 rold = &old->regs[i]; 2137 rcur = &cur->regs[i]; 2138 2139 if (memcmp(rold, rcur, sizeof(*rold)) == 0) 2140 continue; 2141 2142 if (rold->type == NOT_INIT || 2143 (rold->type == UNKNOWN_VALUE && rcur->type != NOT_INIT)) 2144 continue; 2145 2146 if (rold->type == PTR_TO_PACKET && rcur->type == PTR_TO_PACKET && 2147 compare_ptrs_to_packet(rold, rcur)) 2148 continue; 2149 2150 return false; 2151 } 2152 2153 for (i = 0; i < MAX_BPF_STACK; i++) { 2154 if (old->stack_slot_type[i] == STACK_INVALID) 2155 continue; 2156 if (old->stack_slot_type[i] != cur->stack_slot_type[i]) 2157 /* Ex: old explored (safe) state has STACK_SPILL in 2158 * this stack slot, but current has has STACK_MISC -> 2159 * this verifier states are not equivalent, 2160 * return false to continue verification of this path 2161 */ 2162 return false; 2163 if (i % BPF_REG_SIZE) 2164 continue; 2165 if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE], 2166 &cur->spilled_regs[i / BPF_REG_SIZE], 2167 sizeof(old->spilled_regs[0]))) 2168 /* when explored and current stack slot types are 2169 * the same, check that stored pointers types 2170 * are the same as well. 2171 * Ex: explored safe path could have stored 2172 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -8} 2173 * but current path has stored: 2174 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -16} 2175 * such verifier states are not equivalent. 2176 * return false to continue verification of this path 2177 */ 2178 return false; 2179 else 2180 continue; 2181 } 2182 return true; 2183 } 2184 2185 static int is_state_visited(struct verifier_env *env, int insn_idx) 2186 { 2187 struct verifier_state_list *new_sl; 2188 struct verifier_state_list *sl; 2189 2190 sl = env->explored_states[insn_idx]; 2191 if (!sl) 2192 /* this 'insn_idx' instruction wasn't marked, so we will not 2193 * be doing state search here 2194 */ 2195 return 0; 2196 2197 while (sl != STATE_LIST_MARK) { 2198 if (states_equal(&sl->state, &env->cur_state)) 2199 /* reached equivalent register/stack state, 2200 * prune the search 2201 */ 2202 return 1; 2203 sl = sl->next; 2204 } 2205 2206 /* there were no equivalent states, remember current one. 2207 * technically the current state is not proven to be safe yet, 2208 * but it will either reach bpf_exit (which means it's safe) or 2209 * it will be rejected. Since there are no loops, we won't be 2210 * seeing this 'insn_idx' instruction again on the way to bpf_exit 2211 */ 2212 new_sl = kmalloc(sizeof(struct verifier_state_list), GFP_USER); 2213 if (!new_sl) 2214 return -ENOMEM; 2215 2216 /* add new state to the head of linked list */ 2217 memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state)); 2218 new_sl->next = env->explored_states[insn_idx]; 2219 env->explored_states[insn_idx] = new_sl; 2220 return 0; 2221 } 2222 2223 static int do_check(struct verifier_env *env) 2224 { 2225 struct verifier_state *state = &env->cur_state; 2226 struct bpf_insn *insns = env->prog->insnsi; 2227 struct reg_state *regs = state->regs; 2228 int insn_cnt = env->prog->len; 2229 int insn_idx, prev_insn_idx = 0; 2230 int insn_processed = 0; 2231 bool do_print_state = false; 2232 2233 init_reg_state(regs); 2234 insn_idx = 0; 2235 for (;;) { 2236 struct bpf_insn *insn; 2237 u8 class; 2238 int err; 2239 2240 if (insn_idx >= insn_cnt) { 2241 verbose("invalid insn idx %d insn_cnt %d\n", 2242 insn_idx, insn_cnt); 2243 return -EFAULT; 2244 } 2245 2246 insn = &insns[insn_idx]; 2247 class = BPF_CLASS(insn->code); 2248 2249 if (++insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) { 2250 verbose("BPF program is too large. Proccessed %d insn\n", 2251 insn_processed); 2252 return -E2BIG; 2253 } 2254 2255 err = is_state_visited(env, insn_idx); 2256 if (err < 0) 2257 return err; 2258 if (err == 1) { 2259 /* found equivalent state, can prune the search */ 2260 if (log_level) { 2261 if (do_print_state) 2262 verbose("\nfrom %d to %d: safe\n", 2263 prev_insn_idx, insn_idx); 2264 else 2265 verbose("%d: safe\n", insn_idx); 2266 } 2267 goto process_bpf_exit; 2268 } 2269 2270 if (log_level && do_print_state) { 2271 verbose("\nfrom %d to %d:", prev_insn_idx, insn_idx); 2272 print_verifier_state(&env->cur_state); 2273 do_print_state = false; 2274 } 2275 2276 if (log_level) { 2277 verbose("%d: ", insn_idx); 2278 print_bpf_insn(insn); 2279 } 2280 2281 if (class == BPF_ALU || class == BPF_ALU64) { 2282 err = check_alu_op(env, insn); 2283 if (err) 2284 return err; 2285 2286 } else if (class == BPF_LDX) { 2287 enum bpf_reg_type src_reg_type; 2288 2289 /* check for reserved fields is already done */ 2290 2291 /* check src operand */ 2292 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 2293 if (err) 2294 return err; 2295 2296 err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK); 2297 if (err) 2298 return err; 2299 2300 src_reg_type = regs[insn->src_reg].type; 2301 2302 /* check that memory (src_reg + off) is readable, 2303 * the state of dst_reg will be updated by this func 2304 */ 2305 err = check_mem_access(env, insn->src_reg, insn->off, 2306 BPF_SIZE(insn->code), BPF_READ, 2307 insn->dst_reg); 2308 if (err) 2309 return err; 2310 2311 if (BPF_SIZE(insn->code) != BPF_W) { 2312 insn_idx++; 2313 continue; 2314 } 2315 2316 if (insn->imm == 0) { 2317 /* saw a valid insn 2318 * dst_reg = *(u32 *)(src_reg + off) 2319 * use reserved 'imm' field to mark this insn 2320 */ 2321 insn->imm = src_reg_type; 2322 2323 } else if (src_reg_type != insn->imm && 2324 (src_reg_type == PTR_TO_CTX || 2325 insn->imm == PTR_TO_CTX)) { 2326 /* ABuser program is trying to use the same insn 2327 * dst_reg = *(u32*) (src_reg + off) 2328 * with different pointer types: 2329 * src_reg == ctx in one branch and 2330 * src_reg == stack|map in some other branch. 2331 * Reject it. 2332 */ 2333 verbose("same insn cannot be used with different pointers\n"); 2334 return -EINVAL; 2335 } 2336 2337 } else if (class == BPF_STX) { 2338 enum bpf_reg_type dst_reg_type; 2339 2340 if (BPF_MODE(insn->code) == BPF_XADD) { 2341 err = check_xadd(env, insn); 2342 if (err) 2343 return err; 2344 insn_idx++; 2345 continue; 2346 } 2347 2348 /* check src1 operand */ 2349 err = check_reg_arg(regs, insn->src_reg, SRC_OP); 2350 if (err) 2351 return err; 2352 /* check src2 operand */ 2353 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 2354 if (err) 2355 return err; 2356 2357 dst_reg_type = regs[insn->dst_reg].type; 2358 2359 /* check that memory (dst_reg + off) is writeable */ 2360 err = check_mem_access(env, insn->dst_reg, insn->off, 2361 BPF_SIZE(insn->code), BPF_WRITE, 2362 insn->src_reg); 2363 if (err) 2364 return err; 2365 2366 if (insn->imm == 0) { 2367 insn->imm = dst_reg_type; 2368 } else if (dst_reg_type != insn->imm && 2369 (dst_reg_type == PTR_TO_CTX || 2370 insn->imm == PTR_TO_CTX)) { 2371 verbose("same insn cannot be used with different pointers\n"); 2372 return -EINVAL; 2373 } 2374 2375 } else if (class == BPF_ST) { 2376 if (BPF_MODE(insn->code) != BPF_MEM || 2377 insn->src_reg != BPF_REG_0) { 2378 verbose("BPF_ST uses reserved fields\n"); 2379 return -EINVAL; 2380 } 2381 /* check src operand */ 2382 err = check_reg_arg(regs, insn->dst_reg, SRC_OP); 2383 if (err) 2384 return err; 2385 2386 /* check that memory (dst_reg + off) is writeable */ 2387 err = check_mem_access(env, insn->dst_reg, insn->off, 2388 BPF_SIZE(insn->code), BPF_WRITE, 2389 -1); 2390 if (err) 2391 return err; 2392 2393 } else if (class == BPF_JMP) { 2394 u8 opcode = BPF_OP(insn->code); 2395 2396 if (opcode == BPF_CALL) { 2397 if (BPF_SRC(insn->code) != BPF_K || 2398 insn->off != 0 || 2399 insn->src_reg != BPF_REG_0 || 2400 insn->dst_reg != BPF_REG_0) { 2401 verbose("BPF_CALL uses reserved fields\n"); 2402 return -EINVAL; 2403 } 2404 2405 err = check_call(env, insn->imm); 2406 if (err) 2407 return err; 2408 2409 } else if (opcode == BPF_JA) { 2410 if (BPF_SRC(insn->code) != BPF_K || 2411 insn->imm != 0 || 2412 insn->src_reg != BPF_REG_0 || 2413 insn->dst_reg != BPF_REG_0) { 2414 verbose("BPF_JA uses reserved fields\n"); 2415 return -EINVAL; 2416 } 2417 2418 insn_idx += insn->off + 1; 2419 continue; 2420 2421 } else if (opcode == BPF_EXIT) { 2422 if (BPF_SRC(insn->code) != BPF_K || 2423 insn->imm != 0 || 2424 insn->src_reg != BPF_REG_0 || 2425 insn->dst_reg != BPF_REG_0) { 2426 verbose("BPF_EXIT uses reserved fields\n"); 2427 return -EINVAL; 2428 } 2429 2430 /* eBPF calling convetion is such that R0 is used 2431 * to return the value from eBPF program. 2432 * Make sure that it's readable at this time 2433 * of bpf_exit, which means that program wrote 2434 * something into it earlier 2435 */ 2436 err = check_reg_arg(regs, BPF_REG_0, SRC_OP); 2437 if (err) 2438 return err; 2439 2440 if (is_pointer_value(env, BPF_REG_0)) { 2441 verbose("R0 leaks addr as return value\n"); 2442 return -EACCES; 2443 } 2444 2445 process_bpf_exit: 2446 insn_idx = pop_stack(env, &prev_insn_idx); 2447 if (insn_idx < 0) { 2448 break; 2449 } else { 2450 do_print_state = true; 2451 continue; 2452 } 2453 } else { 2454 err = check_cond_jmp_op(env, insn, &insn_idx); 2455 if (err) 2456 return err; 2457 } 2458 } else if (class == BPF_LD) { 2459 u8 mode = BPF_MODE(insn->code); 2460 2461 if (mode == BPF_ABS || mode == BPF_IND) { 2462 err = check_ld_abs(env, insn); 2463 if (err) 2464 return err; 2465 2466 } else if (mode == BPF_IMM) { 2467 err = check_ld_imm(env, insn); 2468 if (err) 2469 return err; 2470 2471 insn_idx++; 2472 } else { 2473 verbose("invalid BPF_LD mode\n"); 2474 return -EINVAL; 2475 } 2476 } else { 2477 verbose("unknown insn class %d\n", class); 2478 return -EINVAL; 2479 } 2480 2481 insn_idx++; 2482 } 2483 2484 verbose("processed %d insns\n", insn_processed); 2485 return 0; 2486 } 2487 2488 /* look for pseudo eBPF instructions that access map FDs and 2489 * replace them with actual map pointers 2490 */ 2491 static int replace_map_fd_with_map_ptr(struct verifier_env *env) 2492 { 2493 struct bpf_insn *insn = env->prog->insnsi; 2494 int insn_cnt = env->prog->len; 2495 int i, j; 2496 2497 for (i = 0; i < insn_cnt; i++, insn++) { 2498 if (BPF_CLASS(insn->code) == BPF_LDX && 2499 (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) { 2500 verbose("BPF_LDX uses reserved fields\n"); 2501 return -EINVAL; 2502 } 2503 2504 if (BPF_CLASS(insn->code) == BPF_STX && 2505 ((BPF_MODE(insn->code) != BPF_MEM && 2506 BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) { 2507 verbose("BPF_STX uses reserved fields\n"); 2508 return -EINVAL; 2509 } 2510 2511 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) { 2512 struct bpf_map *map; 2513 struct fd f; 2514 2515 if (i == insn_cnt - 1 || insn[1].code != 0 || 2516 insn[1].dst_reg != 0 || insn[1].src_reg != 0 || 2517 insn[1].off != 0) { 2518 verbose("invalid bpf_ld_imm64 insn\n"); 2519 return -EINVAL; 2520 } 2521 2522 if (insn->src_reg == 0) 2523 /* valid generic load 64-bit imm */ 2524 goto next_insn; 2525 2526 if (insn->src_reg != BPF_PSEUDO_MAP_FD) { 2527 verbose("unrecognized bpf_ld_imm64 insn\n"); 2528 return -EINVAL; 2529 } 2530 2531 f = fdget(insn->imm); 2532 map = __bpf_map_get(f); 2533 if (IS_ERR(map)) { 2534 verbose("fd %d is not pointing to valid bpf_map\n", 2535 insn->imm); 2536 return PTR_ERR(map); 2537 } 2538 2539 /* store map pointer inside BPF_LD_IMM64 instruction */ 2540 insn[0].imm = (u32) (unsigned long) map; 2541 insn[1].imm = ((u64) (unsigned long) map) >> 32; 2542 2543 /* check whether we recorded this map already */ 2544 for (j = 0; j < env->used_map_cnt; j++) 2545 if (env->used_maps[j] == map) { 2546 fdput(f); 2547 goto next_insn; 2548 } 2549 2550 if (env->used_map_cnt >= MAX_USED_MAPS) { 2551 fdput(f); 2552 return -E2BIG; 2553 } 2554 2555 /* hold the map. If the program is rejected by verifier, 2556 * the map will be released by release_maps() or it 2557 * will be used by the valid program until it's unloaded 2558 * and all maps are released in free_bpf_prog_info() 2559 */ 2560 map = bpf_map_inc(map, false); 2561 if (IS_ERR(map)) { 2562 fdput(f); 2563 return PTR_ERR(map); 2564 } 2565 env->used_maps[env->used_map_cnt++] = map; 2566 2567 fdput(f); 2568 next_insn: 2569 insn++; 2570 i++; 2571 } 2572 } 2573 2574 /* now all pseudo BPF_LD_IMM64 instructions load valid 2575 * 'struct bpf_map *' into a register instead of user map_fd. 2576 * These pointers will be used later by verifier to validate map access. 2577 */ 2578 return 0; 2579 } 2580 2581 /* drop refcnt of maps used by the rejected program */ 2582 static void release_maps(struct verifier_env *env) 2583 { 2584 int i; 2585 2586 for (i = 0; i < env->used_map_cnt; i++) 2587 bpf_map_put(env->used_maps[i]); 2588 } 2589 2590 /* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */ 2591 static void convert_pseudo_ld_imm64(struct verifier_env *env) 2592 { 2593 struct bpf_insn *insn = env->prog->insnsi; 2594 int insn_cnt = env->prog->len; 2595 int i; 2596 2597 for (i = 0; i < insn_cnt; i++, insn++) 2598 if (insn->code == (BPF_LD | BPF_IMM | BPF_DW)) 2599 insn->src_reg = 0; 2600 } 2601 2602 /* convert load instructions that access fields of 'struct __sk_buff' 2603 * into sequence of instructions that access fields of 'struct sk_buff' 2604 */ 2605 static int convert_ctx_accesses(struct verifier_env *env) 2606 { 2607 struct bpf_insn *insn = env->prog->insnsi; 2608 int insn_cnt = env->prog->len; 2609 struct bpf_insn insn_buf[16]; 2610 struct bpf_prog *new_prog; 2611 enum bpf_access_type type; 2612 int i; 2613 2614 if (!env->prog->aux->ops->convert_ctx_access) 2615 return 0; 2616 2617 for (i = 0; i < insn_cnt; i++, insn++) { 2618 u32 insn_delta, cnt; 2619 2620 if (insn->code == (BPF_LDX | BPF_MEM | BPF_W)) 2621 type = BPF_READ; 2622 else if (insn->code == (BPF_STX | BPF_MEM | BPF_W)) 2623 type = BPF_WRITE; 2624 else 2625 continue; 2626 2627 if (insn->imm != PTR_TO_CTX) { 2628 /* clear internal mark */ 2629 insn->imm = 0; 2630 continue; 2631 } 2632 2633 cnt = env->prog->aux->ops-> 2634 convert_ctx_access(type, insn->dst_reg, insn->src_reg, 2635 insn->off, insn_buf, env->prog); 2636 if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) { 2637 verbose("bpf verifier is misconfigured\n"); 2638 return -EINVAL; 2639 } 2640 2641 new_prog = bpf_patch_insn_single(env->prog, i, insn_buf, cnt); 2642 if (!new_prog) 2643 return -ENOMEM; 2644 2645 insn_delta = cnt - 1; 2646 2647 /* keep walking new program and skip insns we just inserted */ 2648 env->prog = new_prog; 2649 insn = new_prog->insnsi + i + insn_delta; 2650 2651 insn_cnt += insn_delta; 2652 i += insn_delta; 2653 } 2654 2655 return 0; 2656 } 2657 2658 static void free_states(struct verifier_env *env) 2659 { 2660 struct verifier_state_list *sl, *sln; 2661 int i; 2662 2663 if (!env->explored_states) 2664 return; 2665 2666 for (i = 0; i < env->prog->len; i++) { 2667 sl = env->explored_states[i]; 2668 2669 if (sl) 2670 while (sl != STATE_LIST_MARK) { 2671 sln = sl->next; 2672 kfree(sl); 2673 sl = sln; 2674 } 2675 } 2676 2677 kfree(env->explored_states); 2678 } 2679 2680 int bpf_check(struct bpf_prog **prog, union bpf_attr *attr) 2681 { 2682 char __user *log_ubuf = NULL; 2683 struct verifier_env *env; 2684 int ret = -EINVAL; 2685 2686 if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS) 2687 return -E2BIG; 2688 2689 /* 'struct verifier_env' can be global, but since it's not small, 2690 * allocate/free it every time bpf_check() is called 2691 */ 2692 env = kzalloc(sizeof(struct verifier_env), GFP_KERNEL); 2693 if (!env) 2694 return -ENOMEM; 2695 2696 env->prog = *prog; 2697 2698 /* grab the mutex to protect few globals used by verifier */ 2699 mutex_lock(&bpf_verifier_lock); 2700 2701 if (attr->log_level || attr->log_buf || attr->log_size) { 2702 /* user requested verbose verifier output 2703 * and supplied buffer to store the verification trace 2704 */ 2705 log_level = attr->log_level; 2706 log_ubuf = (char __user *) (unsigned long) attr->log_buf; 2707 log_size = attr->log_size; 2708 log_len = 0; 2709 2710 ret = -EINVAL; 2711 /* log_* values have to be sane */ 2712 if (log_size < 128 || log_size > UINT_MAX >> 8 || 2713 log_level == 0 || log_ubuf == NULL) 2714 goto free_env; 2715 2716 ret = -ENOMEM; 2717 log_buf = vmalloc(log_size); 2718 if (!log_buf) 2719 goto free_env; 2720 } else { 2721 log_level = 0; 2722 } 2723 2724 ret = replace_map_fd_with_map_ptr(env); 2725 if (ret < 0) 2726 goto skip_full_check; 2727 2728 env->explored_states = kcalloc(env->prog->len, 2729 sizeof(struct verifier_state_list *), 2730 GFP_USER); 2731 ret = -ENOMEM; 2732 if (!env->explored_states) 2733 goto skip_full_check; 2734 2735 ret = check_cfg(env); 2736 if (ret < 0) 2737 goto skip_full_check; 2738 2739 env->allow_ptr_leaks = capable(CAP_SYS_ADMIN); 2740 2741 ret = do_check(env); 2742 2743 skip_full_check: 2744 while (pop_stack(env, NULL) >= 0); 2745 free_states(env); 2746 2747 if (ret == 0) 2748 /* program is valid, convert *(u32*)(ctx + off) accesses */ 2749 ret = convert_ctx_accesses(env); 2750 2751 if (log_level && log_len >= log_size - 1) { 2752 BUG_ON(log_len >= log_size); 2753 /* verifier log exceeded user supplied buffer */ 2754 ret = -ENOSPC; 2755 /* fall through to return what was recorded */ 2756 } 2757 2758 /* copy verifier log back to user space including trailing zero */ 2759 if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) { 2760 ret = -EFAULT; 2761 goto free_log_buf; 2762 } 2763 2764 if (ret == 0 && env->used_map_cnt) { 2765 /* if program passed verifier, update used_maps in bpf_prog_info */ 2766 env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt, 2767 sizeof(env->used_maps[0]), 2768 GFP_KERNEL); 2769 2770 if (!env->prog->aux->used_maps) { 2771 ret = -ENOMEM; 2772 goto free_log_buf; 2773 } 2774 2775 memcpy(env->prog->aux->used_maps, env->used_maps, 2776 sizeof(env->used_maps[0]) * env->used_map_cnt); 2777 env->prog->aux->used_map_cnt = env->used_map_cnt; 2778 2779 /* program is valid. Convert pseudo bpf_ld_imm64 into generic 2780 * bpf_ld_imm64 instructions 2781 */ 2782 convert_pseudo_ld_imm64(env); 2783 } 2784 2785 free_log_buf: 2786 if (log_level) 2787 vfree(log_buf); 2788 free_env: 2789 if (!env->prog->aux->used_maps) 2790 /* if we didn't copy map pointers into bpf_prog_info, release 2791 * them now. Otherwise free_bpf_prog_info() will release them. 2792 */ 2793 release_maps(env); 2794 *prog = env->prog; 2795 kfree(env); 2796 mutex_unlock(&bpf_verifier_lock); 2797 return ret; 2798 } 2799